Pliers and forceps are adapted to numerous special purposes. A simple scissors-action plier such as that shown in U.S. Pat. No. 1,866,771 is formed of two levers with integral jaws, joined at a single pivot, such that the mechanical qualities of the tool are a function of the relative position of the pivot along the lengths of the levers.
Greater leverage can be obtained with a compound linkage in which, typically, one handle and jaw, referred to as the stationary handle and jaw, are integrally joined. The second handle and jaw, referred to as the moveable handle and jaw, are separate pieces. For example, a three link operating linkage is taught in U.S. Pat. No. 1,497,696, where the pair of jaws is connected on a single pivot. The moveable jaw is pivoted at its end to the stationary jaw, while it is pivoted at its shank to an end of the moveable handle. The moveable handle, in turn, is pivoted at its shank to the shank of the stationary handle. This operating linkage has three links, and the pivot at the shanks of the two handles is a sliding pivot point. The mechanical qualities of this tool are a function of both the location of the pivot between the two handles and the location of the pivot between the second handle and moveable jaw.
Another three link system is found in U.S. Pat. No. 1,448,238, in which the moveable jaw is pivoted at its shank to a shank of the stationary jaw. The moveable handle is pivoted at its shank to the shank of the stationary handle. Finally, the end of the stationary jaw is pivoted on a sliding junction to the end of the moveable jaw.
In other variations of plier linkages, the moveable jaw may slide. For example, U.S. Pat. No. 2,167,599 shows a sliding jaw in a tool for coupling railroad cars. Similarly, U.S. Pat. No. 1,935,009 employs a three link system. In this patent, each jaw is integral with its handle, but the shanks of the handles are joined by a pivot link, while the jaws cross at a sliding junction. Still another sliding junction is found in U.S. Pat. No. 2,198,953, wherein the moveable and stationary handles are joined by a toggle link that pushes forward a cam as the handles are closed. In turn, the cam forces the moveable jaw to close along the sliding junction.
Four bar linkages also are used for improved leverage. A four bar linkage in a plier is found in U.S. Pat. No. 1,151,772. A stationary handle and jaw are employed in combination with a moveable handle that is pivoted at its shank to the shank of the stationary handle. The moveable jaw is pivoted at its end, separately to the stationary jaw. Finally, the moveable handle is pivoted at its end to an intermediate link that is also joined to the shank of the moveable jaw. The operating linkage is a parallelogram having equal opposite sides. No sliding pivot point is required, since the parallelogram can change its configuration over a wide range of shapes by pivoting at all four corners.
Another four bar linkage is found in U.S. Pat. No. 1,541,248, in which the moveable handle has the shape of a bell crank. The bend of the crank is pivoted to a rear end of the moveable jaw, while the tip of the crank is pivoted to an end of an intermediate link. This link, in turn, is pivoted at its opposite end to the stationary jaw. The moveable jaw and stationary jaw are joined at their shanks by another pivot.
Still another four bar linkage is found in U.S. Pat. No. 1,219,726, relating to a clamping handle for frying pans. In this patent, the moveable handle again is in the shape of a bell crank. The bend of the crank is pivoted to the stationary handle, while the tip of the crank is pivoted to an end of an intermediate link. The moveable jaw also has a shape similar to a bell crank and is pivoted at its bend to the stationary jaw, while it is pivoted at its rear end to the intermediate link. By this arrangement, closing the handles causes both bell cranks to pivot, closing the jaws.
Many of the pliers of the prior art have good gripping ability and allow application of considerable force. However, they have not been adaptable to certain types of tasks. It would be desirable to have a forceps or plier that not only grips, but also has a grasping motion. In particular, it would be desirable to have a forceps that tends to draw-in the grasped object, as contrasted to merely pinching it. Such a tool should offer action similar to that of the human hand, which draws in a grasped object.
Similarly, a tool employed in surgical procedures should allow careful modulation of applied force. The surgeon must be careful that mechanical tools do not injure a patient due to lack of sensitivity and feel.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the forceps of this invention may comprise the following.